Establishment of high-efficiency Agrobacterium-mediated transformation conditions of soybean callus

The present study was aimed to optimize some transformation conditions for elite Egyptian soybean cultivar Giza 21 using Agrobacterium tumefaciens strain EHA 105. A transformation system was developed using organogenic calli derived from cotyledon and hypocotyl explants on. Murashige and Skoog salts with various concentrations of 2,4-D+0.5 mg L -1 BAP. The calli were inoculated with A. tumefaciens harboring a binary vector with the bar gene and the dicistron containing pr10a and luciferase (luc) genes. The results showed that the number of calli expressing luc gene first increased with inoculation time and bacterial density (OD600) and then dramatically decreased with the increment of both factors. The highest percentage of transformation efficiency (90%) was obtained when the calli explants were inoculated with Agrobacterium for up to 40 min at OD600 of 1.0, followed by 87.5 and 82.5% at OD600 of 0.8 and 1.2, respectively. The transgenes were confirmed in transgenic calli using pr10a and luc primers and gave the expected band size of 480 and 711 bp, respectively. Our results suggested that infection time and Agrobacterium density could have some effects on the transformation efficiency. Furthermore, an effecient Agrobacterium-mediated transformation system was established for soybean callus using dicistronic transformation vector.